Avoid " F I R E" - A little knowledge can save your life

1. Safe Allowable Internal Resistance (in milliohms, mΩ)

The internal resistance (IR) of an 18650 cell is a critical factor in determining its health and safety. Below are general guidelines:

• Notes:
  • IR increases as the battery ages or is damaged.
  • High IR causes heat buildup during charging/discharging, increasing fire risk.
  • Always check the manufacturer’s datasheet for specific tolerances.

2. Weight of the Cell vs. Capacity

The weight of an 18650 cell typically ranges between 45–50 grams, depending on the chemistry (e.g., lithium-ion, lithium-polymer) and capacity.

• Notes:
  • Higher-capacity cells tend to weigh slightly more due to additional active materials.
  • Energy density (Wh/kg) is a key metric for comparing battery performance.

3. Comparison to the “C” Rate

The C-rate indicates how quickly a battery can be charged or discharged relative to its capacity. For example:

• A 1C rate for a 3000 mAh cell means it can safely discharge at 3000 mA (3 A).
• A 2C rate for the same cell means it can discharge at 6000 mA (6 A).

• Notes:
  • Higher C-rates generate more heat, which can increase IR over time.
  • Cells with lower IR can handle higher C-rates more efficiently.

Summary of Key Points

1. Internal Resistance:
   • Safe range: 20–80 mΩ.
   • Replace if >100 mΩ.
   • Fire risk if >150 mΩ.
2. Weight vs. Capacity:
   • Weight: ~45–50 grams.
   • Higher capacity = slightly higher weight but better energy density.
3. C-Rate:
   • Higher C-rates increase heat and IR.
   • Choose cells with low IR for high C-rate applications.

Stay Safe!

This looks like another ChatGPT post. Are we being spammed by LLMs?

I wasn't sure. I though it was informative, and I can't spot something glaringly wrong?

These 'basic knowledge' items should be posted to the knowledge base, and I have no issues if ChatGPT made some contributions there.... as long as everything was checked by actual people who would know better and could correct when it starts hallucinating. 0.

So, I recently got zapped by some shady 18650 battery deals. I bought cells advertised as 3500 mAh, but they turned out to be duds—weighing a measly 41 grams and delivering barely 1800 mAh. Yikes! Turns out, some manufacturers are playing fast and loose with the truth, and it’s not just annoying—it’s downright dangerous.

Imagine slapping these fake cells into a battery pack that needs 3500 mAh to run safely. You could end up with a pack that’s overloaded, overheating, or worse—spicy pillow mode (aka fire). Not exactly the kind of excitement anyone’s looking for!

---

A Little Knowledge Goes a Long Way ​

Here’s the deal:

1. Test your cells! Don’t trust the label—verify the capacity with a good tester.
2. Weight matters! A legit 3500 mAh cell should weigh around 48-50 grams. If it’s lighter, it’s probably a fake.
3. Buy from reputable sellers. Not all Chinese manufacturers are bad—some make fantastic cells. But the shady ones? They’re like battery vampires, sucking your money and leaving you with junk.

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The Plot Twist: Hidden Gems ​

Now, here’s the funny part. I bought a replacement battery pack for my GOTRAX scooter, and when I cracked it open, I found unlabeled cells inside. But surprise! They actually tested at 3550-3650 mAh—better than advertised!

The catch? I have no idea who made them. If anyone knows the manufacturer of these mystery cells, please let me know—I’m looking to buy 1,000 of them!

---

TL;DR​

• Don’t get ripped off by fake 18650 cells. Test them, weigh them, and buy smart.
• Shady batteries = fire hazard. Good batteries = happy life.
• If you know who makes those unlabeled 3550+ mAh cells, hit me up. I need a thousand of those bad boys!

Stay safe, stay charged, and don’t let the battery gremlins win!

Mildly fascinating. I think the way those were generated was that someone took a half-assed post, pasted into some LLM and asked it to rewrite it into a nice forum post. Easy enough to try, huh?

prompt:

Take the following text and turn it into a well formatted forum posts on a DIY e-vehicles forum. Put nice paragraphs and formatting on it, and add a few emojis. Keep the style informal but fix grammar and spelling:

I bought a shit chinese bike the other day, thing was busted, battery was suposed to last for 150km but i only managed like 30. maybe it's because i live on a bog and weve no roads here to speak of, everyone commutes by boat anyway

Click to expand...

generated post:

Bought a Cheap Chinese E-Bike... and It’s Already Busted
So, I picked up a super cheap Chinese e-bike the other day. I knew it wasn’t going to be great, but wow... this thing is busted.

The battery was supposed to last 150 km, but I barely got 30 km out of it. Maybe it’s just false advertising, or maybe it's because I live in a literal bog where roads are basically a myth. Everyone around here commutes by boat, so I guess the bike never really had a chance.

Anyone else had experience with these cheap e-bikes? Worth trying to fix, or should I just strap a boat motor to it and call it a day?

Click to expand...

marvin78 said:

I wasn't sure. I though it was informative, and I can't spot something glaringly wrong?

These 'basic knowledge' items should be posted to the knowledge base, and I have no issues if ChatGPT made some contributions there.... as long as everything was checked by actual people who would know better and could correct when it starts hallucinating. 0.

Click to expand...

Frankly, I do have issues with that. It's honestly much worse than anything a human could write. Sure, it's well formatted and the sentences read nice, but it has 0 individual character, i can't tell people apart if everyone uses it, and we'd end up in a soup of identically-looking meaningless drivel. Just look up and imagine entire threads full of that nonsense, with LLMs responding to one another from tidbits of actual content driving them.

To the OP (and anyone thinking about it): please don't. I'd rather read your original thoughts, spelling mistakes and all. We gain nothing by expressing our thoughts through the word slurry generator.

Well I I do like interacting with personalitites, no really I do, I also like information.

If someone writes a guide with the help of ChatGPT, I will reitterate, I got no issues with that at all. I rather read well written English, which I can understand the exact meaning off, then someone's knowledgable reply if it reads like gibberish.

As I said, as long as the 'chatbot' is giving the right information, I rather have it's output here on the forum then in my own prompt.... because while I might spot some errors it might make, I am 10000000% sure the multitude of people here would correct errors with much greater reliability. Hence, if a 'chatbot' ( or someone with the aid of one ) wrote something and posted it here, and the information is

a> not present yet
b> presented in a manner which conveys the information clearly
c> factually correct, which it will be eventually even if not from the start, because people will come in and comment on the content.

And no so much on the writeup. Or well that's me.

We have a rule against posting LLM output as if it was your own words without any editing.
New rule against AI use on ES

I can tell you didn't proof read or edit the output. You didn't vet the information, and there's numerous mis-statements in it that are the opposite of reality. This is because you didn't read and/or understand the material.

Moving this thread to the dumpster so people reference what NOT to do on this website.
If you do this again, you will be banned.